Circular today becomes the first smart ring to provide a VO2 max estimate, bringing a metric once reserved for lab testing and high-end sports watches to the lightest wearable on the market.

VO2 max is the maximum amount of oxygen your body can use during intense exercise. It is one of the strongest predictors of cardiovascular fitness and longevity. Until now, estimating it required a chest strap, a sports watch with GPS, or a lab visit.

How it works. The Circular Ring calculates your VO2 max estimate using two data points it already tracks continuously: your average resting heart rate (RHR) and your maximum heart rate recorded during activity. The algorithm produces an estimate displayed in the Energy Analysis Circle in the Circular app, updated daily as your fitness evolves.

Where to find it. Open the Energy Analysis Circle. Your VO2 max estimate is displayed alongside your Energy Score and recovery metrics, giving you a complete picture of your readiness for the day.

This is the first time a smart ring has offered this metric without requiring an external device or subscription. No chest strap, no watch, no lab — just the ring on your finger.

Available now for all Circular Ring users.